Anatomy of the mitral subvalvular apparatus

To characterize morphologic variations in the papillary muscles and tendinous cords of the left ventricle and ventricular zones of the mitral valve leaflets.

A total of 100 autopsied human hearts from healthy donors with classical mitral valve type were investigated.

In 1 heart, only 1 group of papillary muscles was found, and in the remaining 99%, we could distinguish 2 groups of muscles: Superolateral (SLPM) and inferoseptal papillary muscle (ISPM) groups. The SLPM group had 1 papillary muscle (75.8%), 2 in 20.2%, and >3 in 4.0%. In the ISPM group, the muscle percentages were 38.4%, 36.4%, and 25.2%, respectively. The apex of at least 1 papillary muscle was situated higher than the plane of the opened anterior leaflet (AML) in 47.5% and 50.5% for the SLPM and ISPM groups, respectively. The number of strut cords arising from the SLPM group was 0 (2.0%), 1 (50.5%), 2 (33.3%), 3 (12.1%), and 4 (2.0%), and from the ISPM group was 0 (6.1%), 1 (52.5%), 2 (35.4%), or 3 (6.1%). Cords to left ventricular outflow tract were present in 14 specimens. Muscular cords were found in eight hearts. In all hearts specimens AML had rough and clear zones. The classical zones (rough, clear, and basal) in the posterior mitral leaflet were observed in 38.4%.

There is a high variability in the papillary muscles and tendinous cords in the mitral valve complex. Proper nomenclature, simple classification, and the most common variants for papillary muscle groups and tendinous cords were presented.